1. Field of the Invention
The present invention relates to a method and apparatus for dynamically allocating resources across multiple virtual machines (VM).
2. Description of Related Art
In the present information technology (IT) industry, virtualization has become a widely used technology. By lowering a customer's total cost of ownership and improving application reliability and flexibility, virtualization technology offers a way to consolidate multiple virtual machines onto a large server. Thus, customers can reduce the need to over-provision resources for individual workload spikes. Moreover, virtualization technology is helpful in isolating important applications, so that different applications running on different virtual machines do not share operating systems. Therefore, a critical failure caused by one application does not affect any of the other applications. This is very critical in today's business environment which requires servers to be continuously running.
IBM has adopted virtualization technology in a number of technical solutions. FIG. 1 shows a system block diagram of an existing Xen virtual machine. In each Xen Host Platform, there are a number of Xen virtual machines. In each virtual machine, an IBM Websphere Application Server (WAS) is running, and a number of business activities are distributed to different virtual machines. In such a scenario, different business activities are categorized and isolated.
Although the existing virtualization technology can categorize and isolate different business activities, the hosting server cannot sense resource requirement changes of each virtual machine in real-time. In the prior art, the resources of the hosting server, such as CPU and memory, are allocated to each virtual machine according to a predetermined static scheme. For example, when a virtual machine is created, the virtual machine is allocated a certain amount of resources, and during the lifecycle of the virtual machine, the resource allocation is usually not changed. However, such a predetermined resource allocation scheme does not meet the requirements of some applications.
FIG. 2 shows a converged and integrated hosting server for a Telecommunications corporation containing different types of services in the prior art. The Web server and the database service are transaction-based services, which can sustain certain delays but are sensitive to transaction failures. On the other hand, the conference server and Session Initiation Protocol (SIP) server are real-time multimedia services, which can sustain certain data loses but are sensitive to data delays. Therefore, in view of resource consumption, the conference service needs a higher priority to guarantee Quality of Service (QoS). But when the conference activity is ended, in order to support lower-priority services, the conference server should release its resources to the other services on the hosting server. However, the currently available virtualization implementations do not support such dynamic resource allocation because the conference server does not release its resources to the other services.